eventchn: one more interface change for luck
eventchn: one more interface change for luck

djs55/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs,euanh/ocaml-xen-lowlevel-libs,jonludlam/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs,euanh/ocaml-xen-lowlevel-libs,euanh/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs